Hi all,
I am having my first problem with my AL-80B and I need some help in
isolating the trouble, along with some signal tracing data that is not covered
in the manual. Below is a synopsis of what is happening.
AMP: 3yr old AL-80B, Amperex 3-500ZG Installed, 110Vac Primary, does not
have the QSK kit installed.
SYMPTOM: With the standby switch in standby, band-switch set for 80M,
AC power applied to Amp, the meters read ~2700Vdc (normal is ~3000Vdc), 150ma
Ip, and the Ig is showing a negative draw. The Ig meter buries itself to the
left. After 2-3 minutes in this condition, the plate is glowing reddish
orange. With the standby switch placed into operate, RF applied from the
exciter, the exciter complains of High SWR and there is no RF power being
produced by the Amp. With the band-switch placed in any other position, the
same symptoms apply.
ASSUMPTION: The 3-500ZG has a short, and or the tube is not receiving
the proper bias voltage during off periods . The glowing while in standby is
due to the current draw across the plate; dissipating ~400W.
HELP: Is my assumption too far fetched? If the tube is shorted, what
could have happened to cause this, considering the tube is only 3yrs of age?
My fear is if I just replace the tube, I will end up back to square one over
time. Is there any trouble shooting guide regarding the Amp? I am looking
for a document or notes indicating voltages, along with tips of what to look
for.
Thank you,
Mike
W5CUL
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